1. Field of the Invention
The present invention is directed to purified or isolated cellulase corresponding to EGVI from Trichoderma spp. The present invention further relates to methods of isolating purified EG VI cellulase obtained from Trichoderma spp. or genetically modified strains of Trichoderma spp. and to methods for using that cellulase in detergents, textile treatment, improving the value of animal feed, processing pulp and paper, grain wet milling and other methods for using cellulase which are known in the art.
2. State of the Art
Cellulases are enzymes which are capable of the hydrolysis of the .beta.-D-glucosidic linkages in celluloses. Cellulolytic enzymes have been traditionally divided into three major classes: endoglucanases, exoglucanases or cellobiohydrolases and .beta.-glucosidases (Knowles, J. et al. (1987), TIBTECH 5, 255-261); and are known to be produced by a large number of bacteria, yeasts and fungi.
Primary among the applications that have been developed for the use of cellulolytic enzymes are those involving degrading (wood)cellulose pulp into sugars for (bio)ethanol production, textile treatments like `stone washing` and `biopolishing`, and in detergent compositions. Thus, cellulases are known to be useful in the treatment of mechanical pulp (see e.g., PCT Publication No. WO 92/16687). Additionally, cellulases are known to be useful as a feed additive (see e.g., PCT Publication No. WO 91/04673) and in grain wet milling.
Of primary importance, however, cellulases are used in the treatment of textiles, i.e., in detergent compositions for assisting in the removal of dirt or grayish cast (see e.g., Great Britain Application Nos. 2,075,028, 2,095,275 and 2,094,826 which illustrate improved cleaning performance when detergents incorporate cellulase) or in the treatment of textiles prior to sale, i.e., for improving the feel and appearance of the textile. Thus, Great Britain Application No. 1,358,599 illustrates the use of cellulase in detergents to reduce the harshness of cotton containing fabrics and cellulases are used in the treatment of textiles to recondition used fabrics by making their colors more vibrant (see e.g., The Shizuoka Prefectural Hammamatsu Textile Industrial Research Institute Report, vol. 24, pp. 54-61 (1986). For example, repeated washing of cotton containing fabrics results in a greyish cast to the fabric which is believed to be due to disrupted and disordered fibrils, sometimes called "pills", caused by mechanical action. This greyish cast is particularly noticeable on colored fabrics. As a consequence, the ability of cellulase to remove the disordered top layer of the fiber and thus improve the overall appearance of the fabric has been of value.
While cellulases are produced (expressed) in fungi, bacteria and the like, cellulase produced by certain fungi, and in particular by the fungal genus Trichoderma spp. (especially Trichoderma longibrachiatum), have been given much attention because a complete cellulase system capable of degrading crystalline forms of cellulose is readily produced in large quantities via fermentation procedures.
Wood et al, "Methods in Enzymology", 160, 25, pages 234 et seq. (1988), disclose that complete fungal cellulase systems comprise several different enzyme classifications including those identified as exo-cellobiohydrolases (EC 3.2.1.91) ("CBH"), endoglucanases (EC 3.2.1.4) ("EG"), and .beta.-glucosidases (EC 3.2.1.21) ("BG"). The fungal cellulase classifications of CBH, EG and BG can be further expanded to include multiple components within each classification. CBHs and EGs have been isolated from a variety of fungal sources. U.S. Pat. No. 5,475,101 (Ward et al.) discloses the purification and molecular cloning of EGIII from Trichoderma longibrachiatum. PCT Publication No. 94/28117 discloses the isolation and sequence of a 20-25 kD cellulase derived from Trichoderma reesei called EGV.
Despite knowledge in the art related to many cellulase compositions having some or all of the above properties, there is a continued need for new cellulases having a varying spectrum of characteristics which are useful in, for example, treating textiles, as a component of detergent compositions, in the treatment of pulp and paper, and in the conversion of biomass. Applicants have discovered a new cellulase isolated from a fermentation broth of Trichoderma longibrachiatum which has heretofore been unknown in the art.